Technical Field
The present invention relates to an image processing device to improve visual recognition of a radiation image, and particularly relates to the image processing device that can provide an image having high visual recognition despite incorporating an image of a metal piece into the radiation image.
Technical Background
A medical facility equips the radiation device to obtain the subject's image using radiation. Such radiographic device comprise the image processing device to display an image having high visual recognition on the monitor by the addition of an image processing on the original image.
The original image prior to image processing is the image as is imaged and the image processing has not been executed yet. Even if the original image as-is displayed on the monitor, the original image having high visual recognition may not be displayed. The image processing device improves the visual recognition of the image incorporated on the monitor by the addition of the image processing on the original image. The image processing device may improve the visual recognition of the image by executing a color tone correction. (Patent Document 1, JP 2007-289687, the entire contents of which are incorporated by reference)
Meantime, in the case of the subject who took a surgery to build up the bone with a metal piece in the past, an image of the metal piece is incorporated into the imaged original image. When the subject having the implanted metal piece inside body is imaged, the hardly radiation transmissive metal piece is obviously incorporated into the original image. The metal piece on the original image appears as an extremely dark image on the original image.
Given the color tone correction is executed without considering the metal piece appeared on the original image, the visual recognition of the image is poorly improved. Because the image processing device improves the visual recognition of the entire image including the extremely dark region of the original image. Therefore, the color tone correction must be performed while excluding the extreme dark region based on the metal piece to assuredly improve the visual recognition of the original image. According to the above method, the color tone correction of the metal piece of the original image would not be executed so that regions other than the metal piece of the original image can be assuredly improved.
Here, as will be noted below, the inventor sets forth the reason why the visual recognition is improved despite color tone correction of only regions other than the metal piece relative to the original image. The metal piece of the original image is not a live tissue of the subject so that it cannot be a focal point of the diagnosis. Specifically, a person in charge of the diagnosis using the image needs to perform a diagnostic imaging of regions other than the metal piece relative to the original image. As set forth above, the color tone correction of regions other than the metal piece relative to the original image is executed so that the visual recognition of the instant regions can be assuredly improved without an impact due to the metal piece relative to the original image. Further, the region subjected to the color tone correction coincides with the regions on which the person in charge of the diagnosis needs to perform the diagnostic imaging. Accordingly, in the case of the original image incorporating the image due to the metal piece, the color tone correction excluding the metal piece can improve further the visual recognition.
First, as set forth above, it must be understood which region of the original image should be assigned as the image due to the metal piece so as to perform the color tone correction excluding the metal piece. The assignment is provided prior to the color tone correction. A graph cut method is applied at this time. The graph cut method is the method to decide whether the instant image of the original image is due to the metal piece or not by considering the brightness of pixels per se constituting the image and the difference of the pixels between the instant pixel and the adjacent pixel thereto.
According to the graph cut method, brightness of the metal piece of the original image must be specified prior to the operation. A region of the metal piece of the original image can be selected to accomplish the specification therefor at this step. The selection requires exactitude. If the selected region includes any non-metal piece region, the aspect recognition of the metal piece based on the graph cut method would be inaccurate so that the bottom-line visual recognition of the image obtained by the color tone correction can be adversely impacted.
A conventional method is utilizing a binarization processing of the image to specify brightness of the metal piece of the original image as set forth above. The metal piece on the original image is extremely dark in the image. Accordingly, the binarization processing is executed so as to let the dark region of the original image come up so that an assignment of the metal piece can be performed.
As set forth above, the case in which the color tone correction is executed relative to the original image is illustrated as an example, the binarization processing is being utilized for an image processing other than the color tone correction. For example, the binarization processing is utilized to prevent that the false image appears in the periphery of metal piece incorporated into the tomographic image formed by executing the image reconstruction processing on the original image continuously imaged while changing the imaging position of the subject. (Patent Document 2, Ser. No. PCT/JP2012/003525)